The subject matter disclosed herein relates to the art of power switching systems and, more particularly, to a power switching system including a micro-electromechanical system array.
Electrical systems employ contacts to switch a flow of current on and off. Contacts are closed to allow passage of the flow of current and open to stop the flow of current. Generally, the contacts may be used in contactors, circuit-breakers, current interrupters, or other electrical devices. A contactor is an electrical device designed to switch an electrical load ON and OFF on command. Traditionally, electromechanical contactors are employed to control operation of various electrical loads such as motors, lights and the like. Depending on their rating, electrical contactors are capable of handling various levels of switching currents. Conventional electromechanical contactors are relatively slow. More specifically, electromechanical contactors take considerable time to open a contact under a fault condition. Under fault condition, more time to open the contact means more fault current passing through a circuit. As such, electromechanical contactors are designed for a high fault current capability to address a worst possible fault current scenario. Given the need to carry high fault currents, convention electromechanical contactors are quite bulky.
As an alternative to slow mechanical and electromechanical switches, fast solid-state switches have been employed in high speed switching applications. As will be appreciated, solid-state switches change between a conducting state and a non-conducting state through controlled application of a voltage or bias. For example, by reverse biasing a solid-state switch, the switch may be transitioned into a non-conducting state. Conventional solid-state switches still lack the desired speed. As such, solid-state switches allow more fault current to flow before any fault is detected and the switch opened.
Switching currents on or off during current flow may produce arcs, or flashes of electricity, which are generally undesirable. To reduce arcs or flashes, both electro-mechanical and sold-state switches open contacts/switched upon sensing a fault condition at a zero crossing of the current in the case of alternating current (AC) systems. In contrast, direct current (DC) typically does not have a zero-crossing point. And hence it is more of a challenge to clear a fault condition. As such, in DC systems, arcs occur at any instance of interruption.
Presently, micro-electrical mechanical system (MEMS) switches are being considered for use in switching systems. Presently, MEMS generally refer to micron-scale structures that for example can integrate a multiplicity of functionally distinct elements, for example, mechanical elements, electromechanical elements, sensors, actuators, and electronics, on a common substrate through micro-fabrication technology. MEMS switches provide a fast response time that is suitable for use in both AC and DC applications. However, MEMS switches are sensitive to arcing. In order to mitigate the arcing, MEMS switches are connected in parallel with a Hybrid Arcless Limiting Technology (HALT) circuit and a Pulse-Assisted Turn On (PATO) circuit. The HALT circuit facilitates arcless opening of the MEMS switches while the PATO circuit facilitates arcless closing of the MEMS switches.